HAZARDOUS DYES

Dyes are basically chemical compounds that can connect themselves to surfaces or fabrics to impart colour. They are complex organic molecules and are required to be resistant to many things such as the action of detergents. Synthetic dyes are widely used in many fields of advanced technology, e.g., in various kinds of the textile, paper, leather tanning, food processing, plastics, cosmetics, rubber, printing and dye manufacturing industries. Synthetic dyes are also in use in ground water tracing, for the determination of specific surface area of activated sludge, sewage and wastewater treatment. (Mustafa T. Yagub 2014)

Adsorption is one of the most effective processes of advanced wastewater treatment which industries employ to reduce hazardous inorganic/organic pollutants present in the effluent. Many textile industries use commercial activated carbon for the treatment of dye waste.

There are several ways for classification of commercial dyes. It can be classified in terms of structure, colour and application methods. However, due to the complexities of the colour nomenclature from the chemical structure system, the classification based on application is often favourable. Several industries such as dye stuff, textile, paper, printing, carpet, plastic, food and cosmetic used dyes to provide colour to their products. These dyes are always left in industrial waste and consequently discharged generally to the water body. (Clarke and Anliker 1980)

Brilliant Green Dye

Brilliant green appears as minute golden crystals and is used in dying silk, wool, leather, jute, and cotton. The dye is considered highly toxic to humans and animals and can cause permanent injury to the eyes of humans and animals. Oral consumption of the dye can cause irritation to the gastrointestinal tract and symptoms like nausea, vomiting, and diarrhoea and may also cause irritation with redness and pain, when it comes in contact with the skin. The dye is also investigated as a mutagen in microorganisms. (Alok Mittal 2008)

Crystal Violet Dye

Crystal violet (CV) is also known as basic violet 3, gentian violet, and methyl violet 10B. CV is used as a pH indicator (yellow to violet with the transition at a pH 1.6). The dye is used as an external skin disinfectant in humans and animals. It is widely used as a purple dye for textiles such as cotton and silk, and in paints and printing ink. The dye is responsible for causing moderate eye irritation, causing painful sensitization to light. It can cause permanent injury to the cornea and conjunctiva since the product contains a cationic dye. It may be absorbed in harmful amounts through the skin and cause skin irritation and digestive tract irritation. In extreme cases it may lead to respiratory and kidney failure and permanent blindness. (Alok Mittal 2010)

Methylene Blue Dye

Methylene blue is the most commonly used substance for dying cotton, wood and silk. Though it is not strongly hazardous, it can cause some harmful effects. Acute exposure to methylene blue can cause increased heart rate, vomiting, shock, Heinz body formation, cyanosis, jaundice, quadriplegia and tissue necrosis in humans. (A. Gurses 2014)

A. Gurses, A. H., M. Kıransan, O. Acisli, S. Karaca (2014). "Removal of methylene blue from aqueous solution using by untreated lignite as potential low-cost adsorbent: Kinetic, thermodynamic and equilibrium approach." Journal of Water Process Engineering.

Alok Mittal, D. K., Jyoti Mittal (2008). "Applicability of waste materials—bottom ash and deoiled soya—as adsorbents for the removal and recovery of a hazardous dye, brilliant green." Journal of Colloid and Interface Science 326: 8-17.

Alok Mittal, J. M., Arti Malviya, Dipika Kaur, V.K. Gupta (2010). "Adsorption of hazardous dye crystal violet from wastewater by waste materials." Journal of Colloid and Interface Science 343: 463-473.

Clarke, E. A. and R. Anliker (1980). Organic Dyes and Pigments. Anthropogenic Compounds, Springer Berlin Heidelberg. 3 / 3A: 181-215.

Mustafa T. Yagub, T. K. S., Sharmeen Afroze, H.M. Ang (2014). "Dye and its removal from aqueous solution by adsorption: A review." Advances in Colloid and Interface Science.